As is well known, heat-sensitive record material generates a colored image by thermally bringing a color former into contact with a color developer, which then developes a color. An advantage of the heat-sensitive record material is that it provides fairly easy maintenance of the recording apparatus. Such materials are now widely used as a recording medium for facsimiles, computer printers and measuring instrument printers.
Known heat-sensitive record materials are mostly those having as a base support sheet materials weighing less 150 g/m.sup.2. This is due to the fact that a heat-sensitive record material in which the base support weighs 150 g/m.sup.2 or more is difficult to stably manufacture, because of problems which can not be easily resolved in the process such as limited fitness of the coating apparatus to be used and the occurrence of curls in the base sheet. In particular, it is difficult to obtain even coating of the surface in the application of the heat-sensitive coating composition onto the base sheet with a bar coater, blade coater, air-knife coater etc. due to the fact that the greater the basis weight of the base sheet becomes the more the contact profile between coater head of the apparatus and the base sheet becomes uneven. In addition, with increases in the basis weight of the base sheet to be used, curls become apt to occur in the assembly obtained.
And, even if a heat-sensitive record material having a thick base sheet of 150 g/m.sup.2 or more could be obtained, it has a tendency to curl during storage or otherwise during the printing operation of facsimile, computer printer, etc.
On the other hand, there is now an increased demand for thick heat-sensitive record materials in various fields and such thick materials particularly usable for tags, tickets, cards, price marks etc.